Five Signs That A Cummins Water Pump Failure is Near

Few things are as devastating to a diesel engine’s performance as the sudden breakdown of the coolant pump. Water pump failure can quickly lead to many other problems, all of which are costly to repair.

On a Cummins engine, water pump failure can mean anything from sudden engine overheat to a literal explosion of parts off of the front of the engine block, depending on the engine in question and the type of failure.

Cummins engine

Drivers and maintenance personnel should do regular maintenance checks and include the water pump in their inspections. Here are five things to look for:

1. Weep Hole Leakage

All water pumps on a diesel engine have a “weep hole” in the water pump housing that is located around the shaft, which may produce a very slow leak. This slow leakage originates from coolant that has passed through the rotating shaft seal. The coolant will “weep” from this location, which is generally found on the underside of the pump housing (when installed).

Although leakage marks from the weep hole do not always mean that the water pump has failed, it is typically a good indicator for shaft seal wear and is the easiest way to visually verify that a water pump is functioning.

2. Leakage From Mounting Surface

Like weep hole leakage, leaks from the mounting surface can be detected visually (in most cases). These leaks may be more persistent or obvious than weep hole leaks. They indicate a more imminent failure and a more serious mechanical problem with the pump itself or its seal to the engine.

3. Loose Attachment To Engine

Any time the water pump is exposed during maintenance or repair, it should be checked for its seal against the block. Physically grabbing the water pump and wiggling it by hand is often the way that a failing – but not quite failed – pump will be detected.

Some pumps will have a viscous seal that doesn’t leak much when operating, even when the pump is loose, but a mechanic’s hand grasping the pump and wiggling up and down or side to side will detect a slight movement. A loose pump is a failure waiting to happen as the pulley/gear will be out of alignment, causing shaft stress and likely changing the pump’s speed intermittently, which can harm the impeller blades.

4. Squeak or Grinding From Gear/Pulley

GMB hd pump

A loose or bad pulley or bad bearings will result in a grinding or squeaking noise when the engine is running. This is most easily detected when the hood is open and a mechanic or driver is standing in front of or beside the engine.

Few diesel engine noises outside of their standard rumble and occasional turbo whine will be heard in the cab, so it’s imperative to get someone to listen to the engine outside if failure is suspected.

5. Corrosion Inside Pump Housing

Less common, but no less telling, are signs of corrosion. Called “cavitation,” this corrosion happens when the coolant mix is not exactly right or when there is a vacuum leak inside the cooling system itself.

The introduction of air to the cooling system will often mean that the higher pressure created by the water pump as it moves the coolant around creates bubbles (“vapor cavities”) in the liquid. These then collapse with small explosions, which can pockmark metal. Those pockmarks, especially when they happen at the pump housing’s seal to the engine block, can then corrode and lead to serious damage.

Any sign of corrosion, including discoloring and a “rough” appearance to the edges of the water pump housing, are a sign that things may be going badly.

Water pump sect

If you experience any one of these 5 symptoms and need to replace the water pump, be sure to get an OEM quality replacement like one of GMB’s heavy duty water pumps. If you have any questions about our HD water pump line, feel free to contact us!


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